Use of vaccine to control and prevent the disease is a vital part of modern human life. However, due to inefficiencies in storage and transport renders a significant percentage of these valuable vaccines ineffective resulting in huge losses in terms of human health and money.
According to a recent meta-analysis published in the journal Vaccine that included studies published in more than 20 countries, it is estimated that a whopping 14 percent (%) to 35% of vaccines are damaged due to temperature excursions beyond the recommended limits during transportation or storage. Such losses can easily translate into thousands of lost human lives and hundreds of millions of dollars of losses due to ineffective treatment and the consequential medical costs.
Usually the technological art of detection of time-temperature indicators known so far can be categorized into three types. This first type (Type 1) uses a visual indicator based on chemical properties that closely match the Arrhenius degradation properties of given material. No equipment is needed to process the indicators. The user does not need to be highly skilled.
On the other hand, the second type (Type 2) relies on electronic circuitry to monitor and log the time-temperature history of the material in interest. Specialized reading equipment is required in this case, which means that the equipment is of larger sizes than Type 1 and the user of the equipment has to be specially trained for interpreting, monitoring and analysis of the data.
The third type (Type 3), although electronic in nature does not keep track of the full history of the temperature variations. In this type of equipment, the apparatus indicates the occurrence of a limited number of pre-determined temperature excursions (for example, the lowest temperature at time T1, medium temperature at time T2, and the like).
The deterioration of simple materials as per Type 1, can be approximated with the well-known Arrhenius equation: K=C.e(−E/(RT)). Here K=rate of deterioration, C is a constant, E is the activation energy of the reaction, R is the universal gas constant, and T is the temperature in Kelvin. However, there is a significant limitation. The complex materials (such as vaccines) are usually not sufficiently characterized by the above equation.
There have been some solutions developed in recent years for monitoring temperature of subject bodies or test materials. For example, in U.S. Pat. No. 6,249,212, there is described a temperature sensing system made from a variety of technologies, i.e., bipolar junction transistors and zener diodes (for voltage regulations), and CMOS (complementary metal-oxide semiconductor) circuits (for data processing and storage, and RF). However, these technologies are cumbersome, and most importantly, the technologies embodied cannot be integrated on a single chip. The electronic system described in the cited patent, due to its complexity, requires large source of power. Alternatively these electronic systems would use visible or infrared source of energy (solar cell) that cannot be integrated on a single chip, due to the use of a mix of technologies; thus the size of the electronic tag is larger and the cost is high.
Further, in U.S. Pat. No. 6,798,219, there is described a temperature monitoring system based on temperature-sensitive metallic mechanical switches (cantilever or bimetallic) or temperature memory alloy. When a pre-established temperature of the subject or target body is reached, the system permanently sets its state. A floating-avalanche MOS (FAMOS) transistor is used to store the state of the system. However, such a system does not store the history of the temperature excursions. The potential drawbacks of the system include higher manufacturing cost due to a combination of metal (made of Aluminum and Silicon, or temperature memory alloy) and electronic devices (Silicon). The disclosed systems may need special casing to isolate the temperature sensing mechanism from the liquid it is immersed in. This is a significant limitation, especially in case, where the subject bodies are vaccines.
Further, in U.S. Patent Application Publication 2010/0170352, there is disclosed a thermistor-based temperature sensing system. RF technology is used to read the temperature from the sensor. The sensor only sends out resistor values, so the calculations for determining the temperature are done using an external system, such as a personal computer (PC). The sensor itself is made of discrete components such as thermistor, related electronics, antenna, and casing. Again, the sensing system requires external power sources. The sensors are required to be placed inside a casing if the temperature of liquids is to be measured. The required casing for insulating the sensors, increases manufacturing cost. On the other hand, the temperature reading may not be as accurate because of the casing.
Further, in U.S. Pat. No. 6,950,028, describes a temperature monitor of electronic nature. It allows user to pre-program the exact thermal characteristics of the material being monitored as compared to the others who rely on simple exponential Arrhenius decay curve. Simple visual indications allow the users to quickly determine the health of the monitored material. This patent included the RFID equipment in the time-temperature scheme as disclosed in U.S. Pat. No. 7,564,364B2.
Further, in PCT Application Publication 2005/106813, describes a temperature monitoring system consisting of a perishable sensor and a RFID transponder to determine the current state of a monitored material state. The time-temperature properties of the material are stored in the memory of the module. The memory is used to lookup the freshness status of the material.
Further, in PCT Application Publication 2008/137409, describes an insulated container fitted with a RFID device which needs a temperature sensors and battery.
Further, in U.S. Pat. No. 8,151,599, describes a transport container for maintaining the material temperature, however does not cover any temperature reading and logging mechanisms.
Further, in U.S. Pat. No. 8,154,421, describes a container with built temperature and location tracking system. An electronic sensor is used for temperature measurement. The GPS components included within the container send out real time data using the cellular communication networks.
Further, in U.S. Patent Application Publication 2010/0021993, describes a method based on impedance measurement of a liquid/material that may not be safe for human to handle or may need to be identified without opening the liquid/material container. The sensor attached to the inside wall of the container has to be insulated from the liquid using a special method and materials. The sensor is attached to a resonant receiver antenna. This antenna is energized by an external transmitting resonant antenna which is coupled with a impedance measurement equipment. The material-sensitive impedance measurement is done by exposing the container to magnetic field.
Further, in U.S. Pat. No. 8,332,240, describes micro electromechanical system (MEMS) and RFID technology in their vaccine tracking monitoring and inventory system. The environmental monitoring tags are based on MEMS. The MEMS are costly as well as not very reliable. The U.S. Patent Application Publication 2013/0316442 suffers from the same drawback.
Further, in E.P. Patent Application Publication 2642436, describes a combination of RFID and wireless technologies.
Further, E.P Granted Patent Number 2435339 and U.S. Patent Application Publication 2013/020309, describe a container with maintained temperatures. The temperature sensing mechanism is based on a thermistor.
These prior art systems have drawbacks in that for example they either use electromagnetic waves which are attenuated by liquid, or require batteries which may cause chemical reactions with liquids and/or do not allow for the monitoring of the temperature fluctuations through time.